Method for reporting mbms information in wireless communication system and device for supporting same

ABSTRACT

Provided is a method for reporting multimedia broadcast and multicast service (MBMS) information by a terminal in a wireless communication system. The method comprises: determining whether or not to perform the logging of MBMS information; logging the MBMS information if the logging is determined to be performed; and reporting the logged MBMS information to a network. Whether or not to perform the logging of the MBMS information is determined on the basis of conditions for performing the logging of the MBMS information. The conditions for performing the logging of the MBMS information comprise the failure of receiving MBMS provided from the network and/or deterioration in the quality of receiving the MBMS.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to wireless communication and, moreparticularly, to a method for reporting Multimedia Broadcast andMulticast Service (MBMS) information in a wireless communication systemand a device supporting the same.

2. Related Art

3rd generation partnership project (3GPP) long term evolution (LTE) isan improved version of a universal mobile telecommunication system(UMTS) and is introduced as the 3GPP release 8. The 3GPP LTE usesorthogonal frequency division multiple access (OFDMA) in a downlink, anduses single carrier-frequency division multiple access (SC-FDMA) in anuplink. The 3GPP LTE employs multiple input multiple output (MIMO)having up to four antennas. In recent years, there is an ongoingdiscussion on 3GPP LTE-advanced (LTE-A) that is an evolution of the 3GPPLTE.

As technologies for supporting wireless communication are advanced, thetype of service that may be provided from a network to users isdiversified. A Multimedia Broadcast and Multicast Service (MBMS) is oneof those services, and provides a terminal with information that may beprovided in TV, movie, and digital forms in a broadcast and/or multicastmanner. The MBMS has a great advantage in excellent efficiency comparedto the case where a network is newly constructed in order to provide aservice in that it can provide a service through the infrastructure ofan already constructed network.

In order to optimize network performance, a network obtains a measuredresult from a terminal. In this case, the network may also obtainlocation information related to the measured result from the terminaland optimize network performance more efficiently. In order to optimizenetworks, service providers may obtain a measured result and locationinformation using a terminal, which is called a Minimization of DrivingTest (MDT).

In order to optimize network performance in relation to the MBMS, anetwork may support an MBMS MDT. The MBMS MDT may include a series ofprocedures, such as a configuration, acquisition, and reporting for MBMSinformation reporting. To this end, the network may select a terminalfor the MBMS information reporting based on the capabilities of aterminal and/or the consent of a terminal user. However, an MBMS serviceis provided on an MBMS Single Frequency Network (MBSFN) area throughbroadcast or multicast, and a terminal that receives the MBMS servicedoes not provide corresponding feedback. Accordingly, a network rarelyobtains information about the MBMS reception status of the terminal.Accordingly, there is a need for a method that enables a network toreceive a report on MBMS information from a terminal.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a method for reportingMultimedia Broadcast and Multicast Service (MBMS) information in awireless communication system and a device supporting the same.

In one aspect, provided is a method of reporting, by user equipment,Multimedia Broadcast and Multicast Service (MBMS) information in awireless communication system. The method includes determining whetheror not to execute a logging of the MBMS information, logging the MBMSinformation if the logging is determined to be performed and reportingthe logged MBMS information to a network. Whether or not to execute thelogging of the MBMS information is determined based on an MBMSinformation logging execution condition. The MBMS information loggingexecution condition comprises at least one of a reception failure of anMBMS service and reception quality of the MBMS service provided by thenetwork.

Determining whether or not to execute the logging of the MBMSinformation may comprise determining to execute the logging if the MBMSinformation logging execution condition is satisfied.

The method may further comprise determining whether or not to stop theexecution of the logging of the MBMS information.

Determining whether or not to stop the execution of the logging of theMBMS information may comprise determining to stop the execution of thelogging if the MBMS information logging execution condition that hasbeen satisfied is released.

Logging the MBMS information may comprise logging a first MBMS log entryif the MBMS information logging execution condition is satisfied andlogging a second MBMS log entry if the MBMS information loggingexecution condition is not satisfied. The logged MBMS information maycomprise the first MBMS log entry and the second MBMS log entry.

The first MBMS log entry may comprise information indicating that thefirst MBMS log entry has been logged because the MBMS informationlogging execution condition has been satisfied.

The second MBMS log entry may comprise information indicating that thesecond MBMS log entry has been logged because the satisfaction of theMBMS information logging execution condition has been released.

Logging the MBMS information may comprise periodically logging thirdMBMS log entries until the satisfaction of the MBMS information loggingexecution condition is released after the MBMS information loggingexecution condition is satisfied. The logged MBMS information mayfurther comprise the third MBMS log entries.

Each of the third MBMS log entries may comprise information indicatingthat a corresponding third MBMS log entry has been periodically logged.

The method may further comprise receiving an MBMS reportingconfiguration comprising configuration information for the logging andreporting of the MBMS information by the user equipment from thenetwork. The MBMS reporting configuration may comprise MBMS loggingexecution information which specifies the MBMS information loggingexecution condition.

Reporting the logged MBMS information to the network may comprisesending a logged MBMS information availability indicator indicating thatthe logged MBMS information to be reported to the network is present tothe network, receiving a logged MBMS information reporting request whichrequests the reporting of the logged MBMS information from the networkand sending a logged MBMS information report comprising the logged MBMSinformation to the network in response to the logged MBMS informationreporting request.

Reporting the logged MBMS information to the network may compriseimmediately sending the logged MBMS information to the network inresponse to the logging of the MBMS information.

In another aspect, provided is a wireless device operating in a wirelesscommunication system. The wireless device comprises a Radio Frequency(RF) unit which sends and receives radio signals and a processor whichis functionally coupled to the RF unit and operates. The processor isconfigured to: determine whether or not to execute a logging of the MBMSinformation, log the MBMS information if the logging is determined to beperformed and report the logged MBMS information to a network. Whetheror not to execute the logging of the MBMS information is determinedbased on an MBMS information logging execution condition. The MBMSinformation logging execution condition comprises at least one of areception failure of an MBMS service and reception quality of the MBMSservice provided by the network.

In accordance with the method of reporting MBMS information according toan embodiment of the present invention, UE configured to report MBMSinformation can obtain and log MBMS information depending on thereception status or reception quality status of an MBMS service.Accordingly, a problem in which unnecessary power is consumed because UEobtains and logs MBMS information in the situation in which an MBMSservice not related to the UE is provided or the UE is not provided withan MBMS service can be prevented. Furthermore, signaling overhead can bereduced because unnecessary signaling for reporting MBMS information byUE can be prevented, and thus use efficiency of radio resources can beimproved.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a wireless communication system to which the presentinvention is applied.

FIG. 2 is a block diagram showing the structure of a wireless protocolon the user plane.

FIG. 3 is a block diagram showing the structure of a wireless protocolon the control plane.

FIG. 4 is a flowchart illustrating the operation of UE in the RRC idlestate.

FIG. 5 is a flowchart illustrating a process of establishing RRCconnection.

FIG. 6 is a flowchart illustrating an RRC connection reconfigurationprocess.

FIG. 7 is a diagram illustrating an RRC connection re-establishmentprocedure.

FIG. 8 is a flowchart illustrating a measuring method according to therelated art.

FIG. 9 illustrates an example of measurement configuration in theterminal.

FIG. 10 illustrates an example of removing the measurement identity.

FIG. 11 illustrates an example of removing the measurement object.

FIG. 12 is a flowchart illustrating a method for performing a loggedMDT.

FIG. 13 is a diagram illustrating an example of a logged MDT accordingto a logging area.

FIG. 14 is a diagram illustrating an example of a logged MDT accordingto a change of an RAT.

FIG. 15 is a diagram illustrating an example of logged measurements.

FIG. 16 is a diagram illustrating an example of an immediate MDT.

FIG. 17 is a diagram illustrating a method for reporting MBMSinformation in accordance with an embodiment of the present invention.

FIG. 18 is a diagram illustrating an example of a method for reportingMBMS information in accordance with an embodiment of the presentinvention.

FIG. 19 is a diagram illustrating another example of a method forreporting MBMS information in accordance with an embodiment of thepresent invention.

FIG. 20 is a block diagram illustrating a wireless device in which anembodiment of the present invention is implemented.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

FIG. 1 shows a wireless communication system to which the presentinvention is applied. The wireless communication system may also bereferred to as an evolved-UMTS terrestrial radio access network(E-UTRAN) or a long term evolution (LTE)/LTE-A system.

The E-UTRAN includes at least one base station (BS) 20 which provides acontrol plane and a user plane to a user equipment (UE) 10. The UE 10may be fixed or mobile, and may be referred to as another terminology,such as a mobile station (MS), a user terminal (UT), a subscriberstation (SS), a mobile terminal (MT), a wireless device, etc. The BS 20is generally a fixed station that communicates with the UE 10 and may bereferred to as another terminology, such as an evolved node-B (eNB), abase transceiver system (BTS), an access point, etc.

The BSs 20 are interconnected by means of an X2 interface. The BSs 20are also connected by means of an S1 interface to an evolved packet core(EPC) 30, more specifically, to a mobility management entity (MME)through Sl-MME and to a serving gateway (S-GW) through Sl-U.

The EPC 30 includes an MME, an S-GW, and a packet data network-gateway(P-GW). The MME has access information of the UE or capabilityinformation of the UE, and such information is generally used formobility management of the UE. The S-GW is a gateway having an E-UTRANas an end point. The P-GW is a gateway having a PDN as an end point.

Layers of a radio interface protocol between the UE and the network canbe classified into a first layer (L1), a second layer (L2), and a thirdlayer (L3) based on the lower three layers of the open systeminterconnection (OSI) model that is well-known in the communicationsystem. Among them, a physical (PHY) layer belonging to the first layerprovides an information transfer service by using a physical channel,and a radio resource control (RRC) layer belonging to the third layerserves to control a radio resource between the UE and the network. Forthis, the RRC layer exchanges an RRC message between the UE and the BS.

FIG. 2 is a diagram showing a wireless protocol architecture for a userplane. FIG. 3 is a diagram showing a wireless protocol architecture fora control plane. The user plane is a protocol stack for user datatransmission. The control plane is a protocol stack for control signaltransmission.

Referring to FIGS. 2 and 3, a PHY layer provides an upper layer with aninformation transfer service through a physical channel. The PHY layeris connected to a medium access control (MAC) layer which is an upperlayer of the PHY layer through a transport channel. Data is transferredbetween the MAC layer and the PHY layer through the transport channel.The transport channel is classified according to how and with whatcharacteristics data is transferred through a radio interface.

Data is moved between different PHY layers, that is, the PHY layers of atransmitter and a receiver, through a physical channel. The physicalchannel may be modulated according to an Orthogonal Frequency DivisionMultiplexing (OFDM) scheme, and use the time and frequency as radioresources.

The functions of the MAC layer include mapping between a logical channeland a transport channel and multiplexing and demultiplexing to atransport block that is provided through a physical channel on thetransport channel of a MAC Service Data Unit (SDU) that belongs to alogical channel. The MAC layer provides service to a Radio Link Control(RLC) layer through the logical channel.

The functions of the RLC layer include the concatenation, segmentation,and reassembly of an RLC SDU. In order to guarantee various types ofQuality of Service (QoS) required by a Radio Bearer (RB), the RLC layerprovides three types of operation mode: Transparent Mode (TM),Unacknowledged Mode (UM), and Acknowledged Mode (AM). AM RLC provideserror correction through an Automatic Repeat Request (ARQ).

The RRC layer is defined only on the control plane. The RRC layer isrelated to the configuration, reconfiguration, and release of radiobearers, and is responsible for control of logical channels, transportchannels, and PHY channels. An RB means a logical route that is providedby the first layer (PHY layer) and the second layers (MAC layer, the RLClayer, and the PDCP layer) in order to transfer data between UE and anetwork.

The function of a Packet Data Convergence Protocol (PDCP) layer on theuser plane includes the transfer of user data and header compression andciphering. The function of the PDCP layer on the user plane furtherincludes the transfer and encryption/integrity protection of controlplane data.

What an RB is configured means a process of defining the characteristicsof a wireless protocol layer and channels in order to provide specificservice and configuring each detailed parameter and operating method. AnRB can be divided into two types of a Signaling RB (SRB) and a Data RB(DRB). The SRB is used as a passage through which an RRC message istransmitted on the control plane, and the DRB is used as a passagethrough which user data is transmitted on the user plane.

If RRC connection is established between the RRC layer of UE and the RRClayer of an E-UTRAN, the UE is in the RRC connected state. If not, theUE is in the RRC idle state.

A downlink transport channel through which data is transmitted from anetwork to UE includes a broadcast channel (BCH) through which systeminformation is transmitted and a downlink shared channel (SCH) throughwhich user traffic or control messages are transmitted. Traffic or acontrol message for downlink multicast or broadcast service may betransmitted through the downlink SCH, or may be transmitted through anadditional downlink multicast channel (MCH). Meanwhile, an uplinktransport channel through which data is transmitted from UE to a networkincludes a random access channel (RACH) through which an initial controlmessage is transmitted and an uplink shared channel (SCH) through whichuser traffic or control messages are transmitted.

Logical channels that are placed over the transport channel and that aremapped to the transport channel include a broadcast control channel(BCCH), a paging control channel (PCCH), a common control channel(CCCH), a multicast control channel (MCCH), and a multicast trafficchannel (MTCH).

The physical channel includes several OFDM symbols in the time domainand several subcarriers in the frequency domain. One subframe includes aplurality of OFDM symbols in the time domain. An RB is a resourcesallocation unit, and includes a plurality of OFDM symbols and aplurality of subcarriers. Furthermore, each subframe may use specificsubcarriers of specific OFDM symbols (e.g., the first OFDM symbol) ofthe corresponding subframe for a physical downlink control channel(PDCCH), that is, an L1/L2 control channel. A Transmission Time Interval(TTI) is a unit time for subframe transmission.

As disclosed in 3GPP TS 36.211 V8.7.0, a physical channel in a 3GPP LTEmay be divided into a PDSCH (Physical Downlink Shared Channel) and aPUSCH (Physical Uplink Shared Channel) being a data channel and a PDCCH(Physical Downlink Control Channel), a PCFICH (Physical Control FormatIndicator Channel), a PHICH (Physical Hybrid-ARQ Indicator Channel), anda PUCCH (Physical Uplink Control Channel) being a control channel.

A PCFICH transmitted through a first OFDM symbol of a sub-frame carriesa CFI (control format indicator) with respect to the number of OFDMsymbols used to transmit control channels in a sub-frame. The terminalfirstly receives a CFI on a PCFICH to monitor the PDCCH.

The PDCCH refers to a scheduling channel to carry schedule informationas a downlink control channel. The control information transmittedthrough the PDCCH refers to downlink control information (DCI). The DCImay include resource allocation of the PDSCH (refers to DL grant(downlink grant)), resource allocation of the PUSCH (refers to uplink(UL) grant)), and a group and/or VoIP (Voice over Internet Protocol) ofa transmission power control command with respect to individual UEs inan optional UE group.

In the 3GPP LTE, blind decoding is used to detect the PDCCH. The blinddecoding de-masks a desired identifier to a CRC (Cyclic RedundancyCheck) of a received PDCCH (refers to candidate PDCCH), and checks a CRCerror to determine whether a corresponding PDCCH is a control channelthereof.

The base station determines a PDCCH format according to a DCI to be sentto the terminal to attach a CRC to the DCI, and masks a uniqueidentifier (refers to RNTI (Radio Network Temporary Identifier))according to an owner or a use of the PDCCH.

The RRC state of UE and an RRC connection method are described below.

The RRC state means whether or not the RRC layer of UE is logicallyconnected to the RRC layer of the E-UTRAN. A case where the RRC layer ofUE is logically connected to the RRC layer of the E-UTRAN is referred toas an RRC connected state. A case where the RRC layer of UE is notlogically connected to the RRC layer of the E-UTRAN is referred to as anRRC idle state. The E-UTRAN may check the existence of corresponding UEin the RRC connected state in each cell because the UE has RRCconnection, so the UE may be effectively controlled. In contrast, theE-UTRAN is unable to check UE in the RRC idle state, and a Core Network(CN) manages UE in the RRC idle state in each tracking area, that is,the unit of an area greater than a cell. That is, the existence ornon-existence of UE in the RRC idle state is checked only for each largearea. Accordingly, the UE needs to shift to the RRC connected state inorder to be provided with common mobile communication service, such asvoice or data.

When a user first powers UE, the UE first searches for a proper cell andremains in the RRC idle state in the corresponding cell. The UE in theRRC idle state establishes RRC connection with an E-UTRAN through an RRCconnection procedure when it is necessary to set up the RRC connection,and shifts to the RRC connected state. A case where UE in the RRC idlestate needs to set up RRC connection includes several cases. Forexample, the cases may include a need to send uplink data for a reason,such as a call attempt by a user, and to send a response message as aresponse to a paging message received from an E-UTRAN.

A Non-Access Stratum (NAS) layer placed over the RRC layer performsfunctions, such as session management and mobility management.

In the NAS layer, in order to manage the mobility of UE, two types ofstates: EPS Mobility Management-REGISTERED (EMM-REGISTERED) andEMM-DEREGISTERED are defined. The two states are applied to UE and theMME. UE is initially in the EMM-DEREGISTERED state. In order to access anetwork, the UE performs a process of registering it with thecorresponding network through an initial attach procedure. If the attachprocedure is successfully performed, the UE and the MME become theEMM-REGISTERED state.

In order to manage signaling connection between UE and the EPC, twotypes of states: an EPS Connection Management (ECM)-IDLE state and anECM-CONNECTED state are defined. The two states are applied to UE andthe MME. When the UE in the ECM-IDLE state establishes RRC connectionwith the E-UTRAN, the UE becomes the ECM-CONNECTED state. The MME in theECM-IDLE state becomes the ECM-CONNECTED state when it establishes SIconnection with the E-UTRAN. When the UE is in the ECM-IDLE state, theE-UTRAN does not have information about the context of the UE.Accordingly, the UE in the ECM-IDLE state performs procedures related toUE-based mobility, such as cell selection or cell reselection, without aneed to receive a command from a network. In contrast, when the UE is inthe ECM-CONNECTED state, the mobility of the UE is managed in responseto a command from a network. If the location of the UE in the ECM-IDLEstate is different from a location known to the network, the UE informsthe network of its corresponding location through a tracking area updateprocedure.

System information is described below.

System information includes essential information that needs to be knownby UE in order for the UE to access a BS. Accordingly, the UE needs tohave received all pieces of system information before accessing the BS,and needs to always have the up-to-date system information. Furthermore,the BS periodically transmits the system information because the systeminformation is information that needs to be known by all UEs within onecell. The system information is divided into a MIB (Master InformationBlock) and a plurality of SIBs (System Information Blocks).

The MIB may include a limited number of parameters which are mostfrequently transmitted and are required for acquisition for otherinformation from a cell. The terminal firstly searches the MIB afterdownlink synchronization. The MIB may include information such as adownlink channel bandwidth, PHICH configuration, an SFN to supportsynchronization and to be operated as a timing reference, and eNBtransmission antenna configuration. The MIB may be broadcasted on theBCH.

A SIB1 (SystemInformationBlockType1) among SIBs is transmitted whilebeing included in a SystemInformationBlockType1, and other SIBs exceptfor the SIB1 is transmitted while being included in the systeminformation message. The SIBs may be flexibly mapped to the systeminformation message according to a scheduling information list parameterincluded in the SIB1. However, each SIB is included in a single systeminformation message, and only SIBs having the same scheduling requiredvalue (e.g. period) may be mapped to the same system informationmessage. Further, a SIB2 (SystemInformationBlockType2) is mapped to asystem information message corresponding to a first entry in a systeminformation message list of a scheduling information list. A pluralityof system information messages may be transmitted within the same timeperiod. The SIB1 and all system information messages are transmitted ona DL-SCH.

Further to broadcast transmission, the E-UTRAN may be dedicated-signaledin a state that the SIB1 includes the same parameter as apreconfiguration value. In this case, the SIB1 may be transmitted whilebeing included in a RRC connection reconfiguration message.

The SIB1 includes information on terminal cell access, and definesscheduling of other SIBs. The SIB1 may include PLMN identifiers of anetwork, a TAC (Tracking Area Code), a cell ID, a cell barring status toindicate whether a cell may camp-on, the lowest reception level requiredin a cell used as a cell reselection reference, and information on atransmission time and a time period of other SIBs.

The SIB2 may include radio resource configuration information common inall terminals. The SIB2 may include a uplink carrier frequency, anuplink channel bandwidth, RACH configuration, paging configuration,uplink power control configuration, sounding reference signalconfiguration, PUCCH configuration and PUSCH configuration supportingACK/NACK transmission.

The terminal may apply acquisition and change sensing procedures ofsystem information with respect to only a PCell. In the SCell, theE-UTRAN may provide all system information on the RRC connection stateoperation through dedicated signaling when a corresponding SCell isadded. When system information on the configured SCell is changed, theE-UTRAN may release a considered SCell and may add the considered SCelllater, which may be performed together with a single RRC connectionreconfiguration message. The E-UTRAN may configure parameter valuesdifferent from a value broadcasted in the considered SCell through thededicated signaling.

The terminal should ensure validity with respect to system informationof a specific type. The above system information refers to requiredsystem information. The required system information may be defined asfollows.

-   -   When the terminal is in a RRC idle state: the terminal should to        have a valid version of an MIB and the SIB1 as well as a SIB2 to        a SIBS, which may depend on support of a considered RAT.    -   When the terminal is in a RRC connection state: the terminal        should ensure to have valid versions of the MIB, the SIB1 and        the SIB2.

In general, after the system information is acquired, validity may beensured with a maximum three hours.

In general, service that is provided to UE by a network may beclassified into three types as follows. Furthermore, the UE differentlyrecognizes the type of cell depending on what service may be provided tothe UE. In the following description, a service type is first described,and the type of cell is described.

1) Limited service: this service provides emergency calls and anEarthquake and Tsunami Warning System (ETWS), and may be provided by anacceptable cell.

2) Suitable service: this service means public service for common uses,and may be provided by a suitable cell (or a normal cell).

3) Operator service: this service means service for communicationnetwork operators. This cell may be used by only communication networkoperators, but may not be used by common users.

In relation to a service type provided by a cell, the type of cell maybe classified as follows.

1) An acceptable cell: this cell is a cell from which UE may be providedwith limited service. This cell is a cell that has not been barred froma viewpoint of corresponding UE and that satisfies the cell selectioncriterion of the UE.

2) A suitable cell: this cell is a cell from which UE may be providedwith suitable service. This cell satisfies the conditions of anacceptable cell and also satisfies additional conditions. The additionalconditions include that the suitable cell needs to belong to a PublicLand Mobile Network (PLMN) to which corresponding UE may access and thatthe suitable cell is a cell on which the execution of a tracking areaupdate procedure by the UE is not barred. If a corresponding cell is aCSG cell, the cell needs to be a cell to which UE may access as a memberof the CSG.

3) A barred cell: this cell is a cell that broadcasts informationindicative of a barred cell through system information.

4) A reserved cell: this cell is a cell that broadcasts informationindicative of a reserved cell through system information.

FIG. 4 is a flowchart illustrating the operation of UE in the RRC idlestate. FIG. 4 illustrates a procedure in which UE that is initiallypowered on experiences a cell selection process, registers it with anetwork, and then performs cell reselection if necessary.

Referring to FIG. 4, the UE selects Radio Access Technology (RAT) inwhich the UE communicates with a Public Land Mobile Network (PLMN), thatis, a network from which the UE is provided with service (S410).Information about the PLMN and the RAT may be selected by the user ofthe UE, and the information stored in a Universal Subscriber IdentityModule (USIM) may be used.

The UE selects a cell that has the greatest value and that belongs tocells having measured BS and signal intensity or quality greater than aspecific value (cell selection) (S420). In this case, the UE that ispowered off performs cell selection, which may be called initial cellselection. A cell selection procedure is described later in detail.After the cell selection, the UE receives system informationperiodically by the BS. The specific value refers to a value that isdefined in a system in order for the quality of a physical signal indata transmission/reception to be guaranteed. Accordingly, the specificvalue may differ depending on applied RAT.

If network registration is necessary, the UE performs a networkregistration procedure (S430). The UE registers its information (e.g.,an IMSI) with the network in order to receive service (e.g., paging)from the network. The UE does not register it with a network whenever itselects a cell, but registers it with a network when information aboutthe network (e.g., a Tracking Area Identity (TAI)) included in systeminformation is different from information about the network that isknown to the UE.

The UE performs cell reselection based on a service environment providedby the cell or the environment of the UE (S440). If the value of theintensity or quality of a signal measured based on a BS from which theUE is provided with service is lower than that measured based on a BS ofa neighboring cell, the UE selects a cell that belongs to other cellsand that provides better signal characteristics than the cell of the BSthat is accessed by the UE. This process is called cell reselectiondifferently from the initial cell selection of the No. 2 process. Inthis case, temporal restriction conditions are placed in order for acell to be frequently reselected in response to a change of signalcharacteristic. A cell reselection procedure is described later indetail.

FIG. 5 is a flowchart illustrating a process of establishing RRCconnection.

UE sends an RRC connection request message that requests RRC connectionto a network (S510). The network sends an RRC connection establishmentmessage as a response to the RRC connection request (S520). Afterreceiving the RRC connection establishment message, the UE enters RRCconnected mode.

The UE sends an RRC connection establishment complete message used tocheck the successful completion of the RRC connection to the network(S530).

FIG. 6 is a flowchart illustrating an RRC connection reconfigurationprocess. An RRC connection reconfiguration is used to modify RRCconnection. This is used to establish/modify/release RBs, performhandover, and set up/modify/release measurements.

A network sends an RRC connection reconfiguration message for modifyingRRC connection to UE (S610). As a response to the RRC connectionreconfiguration message, the UE sends an RRC connection reconfigurationcomplete message used to check the successful completion of the RRCconnection reconfiguration to the network (S620).

Hereinafter, a public land mobile network (PLMN) is described.

The PLMN is a network which is disposed and operated by a mobile networkoperator. Each mobile network operator operates one or more PLMNs. EachPLMN may be identified by a Mobile Country Code (MCC) and a MobileNetwork Code (MNC). PLMN information of a cell is included in systeminformation and broadcasted.

In PLMN selection, cell selection, and cell reselection, various typesof PLMNs may be considered by the terminal.

Home PLMN (HPLMN): PLMN having MCC and MNC matching with MCC and MNC ofa terminal IMSI.

Equivalent HPLMN (EHPLMN): PLMN serving as an equivalent of an HPLMN.

Registered PLMN (RPLMN): PLMN successfully finishing locationregistration.

Equivalent PLMN (EPLMN): PLMN serving as an equivalent of an RPLMN.

Each mobile service consumer subscribes in the HPLMN. When a generalservice is provided to the terminal through the HPLMN or the EHPLMN, theterminal is not in a roaming state. Meanwhile, when the service isprovided to the terminal through a PLMN except for the HPLMN/EHPLMN, theterminal is in the roaming state. In this case, the PLMN refers to aVisited PLMN (VPLMN).

When UE is initially powered on, the UE searches for available PublicLand Mobile Networks (PLMNs) and selects a proper PLMN from which the UEis able to be provided with service. The PLMN is a network that isdeployed or operated by a mobile network operator. Each mobile networkoperator operates one or more PLMNs. Each PLMN may be identified byMobile Country Code (MCC) and Mobile Network Code (MNC). Informationabout the PLMN of a cell is included in system information andbroadcasted. The UE attempts to register it with the selected PLMN. Ifregistration is successful, the selected PLMN becomes a Registered PLMN(RPLMN). The network may signalize a PLMN list to the UE. In this case,PLMNs included in the PLMN list may be considered to be PLMNs, such asRPLMNs. The UE registered with the network needs to be able to be alwaysreachable by the network. If the UE is in the ECM-CONNECTED state(identically the RRC connection state), the network recognizes that theUE is being provided with service. If the UE is in the ECM-IDLE state(identically the RRC idle state), however, the situation of the UE isnot valid in an eNB, but is stored in the MME. In such a case, only theMME is informed of the location of the UE in the ECM-IDLE state throughthe granularity of the list of Tracking Areas (TAs). A single TA isidentified by a Tracking Area Identity (TAI) formed of the identifier ofa PLMN to which the TA belongs and Tracking Area Code (TAC) thatuniquely expresses the TA within the PLMN.

Thereafter, the UE selects a cell that belongs to cells provided by theselected PLMN and that has signal quality and characteristics on whichthe UE is able to be provided with proper service.

The following is a detailed description of a procedure of selecting acell by a terminal.

When power is turned-on or the terminal is located in a cell, theterminal performs procedures for receiving a service byselecting/reselecting a suitable quality cell.

A terminal in an RRC idle state should prepare to receive a servicethrough the cell by always selecting a suitable quality cell. Forexample, a terminal where power is turned-on just before should selectthe suitable quality cell to be registered in a network. If the terminalin an RRC connection state enters in an RRC idle state, the terminalshould selects a cell for stay in the RRC idle state. In this way, aprocedure of selecting a cell satisfying a certain condition by theterminal in order to be in a service idle state such as the RRC idlestate refers to cell selection. Since the cell selection is performed ina state that a cell in the RRC idle state is not currently determined,it is important to select the cell as rapid as possible. Accordingly, ifthe cell provides a wireless signal quality of a predetermined level orgreater, although the cell does not provide the best wireless signalquality, the cell may be selected during a cell selection procedure ofthe terminal.

A method and a procedure of selecting a cell by a terminal in a 3GPP LTEis described with reference to 3GPP TS 36.304 V8.5.0 (2009-03) “UserEquipment (UE) procedures in idle mode (Release 8)”.

A cell selection process is basically divided into two types.

The first is an initial cell selection process. In this process, UE doesnot have preliminary information about a wireless channel. Accordingly,the UE searches for all wireless channels in order to find out a propercell. The UE searches for the strongest cell in each channel.Thereafter, if the UE has only to search for a suitable cell thatsatisfies a cell selection criterion, the UE selects the correspondingcell.

Next, the UE may select the cell using stored information or usinginformation broadcasted by the cell. Accordingly, cell selection may befast compared to an initial cell selection process. If the UE has onlyto search for a cell that satisfies the cell selection criterion, the UEselects the corresponding cell. If a suitable cell that satisfies thecell selection criterion is not retrieved though such a process, the UEperforms an initial cell selection process.

A cell selection reference may be defined as expressed by a followingequation 1.

Srxlev>0 AND Squal>0   [Equation 1]

where:

Srxlev=Q _(rxlevmeas)−(Q _(rxlevmin) +Q _(rxlevminoffset))−Pcompensation

Squal=Q _(qualmeas)−(Q _(qualmin) +Q _(qualminoffset))

In this case, respective variables of the equation I may be defined by afollowing table 1.

TABLE 1 Srxlev Cell selection RX level value (dB) Squal Cell selectionquality value (dB) Q_(rxlevmeas) Measured cell RX level value (RSRP)Q_(qualmeas) Measured cell quality value (RSRQ) Q_(rxlevmin) Minimumrequired RX level in the cell (dBm) Q_(qualmin) Minimum required qualitylevel in the cell (dB) Q_(rxlevminoffset) Offset to the signalledQ_(rxlevmin) taken into account in the Srxlev evaluation as a result ofa periodic search for a higher priority PLMN while camped normally in aVPLMN [5] Q_(qualminoffset) Offset to the signalled Q_(qualmin) takeninto account in the Squal evaluation as a result of a periodic searchfor a higher priority PLMN while camped normally in a VPLMN [5]Pcompensation max(P_(EMAX) − P_(PowerClass), 0) (dB) P_(EMAX) Maximum TXpower level an UE may use when transmitting on the uplink in the cell(dBm) defined as P_(EMAX) in [TS 36.101] P_(PowerClass) Maximum RFoutput power of the UE (dBm) according to the UE power class as definedin [TS 36.101]

Signaled values Qrxlevminoffset and Qqualminoffset are a result ofperiodic search with respect to a PLMN of a higher priority while theterminal camps on a normal cell in the VPLMN. During the periodic searchwith the PLMN having the higher priority, the terminal may perform cellselection estimation using stored parameters from other cell of the PLMNhaving the higher priority.

After the UE selects a specific cell through the cell selection process,the intensity or quality of a signal between the UE and a BS may bechanged due to a change in the mobility or wireless environment of theUE. Accordingly, if the quality of the selected cell is deteriorated,the UE may select another cell that provides better quality. If a cellis reselected as described above, the UE selects a cell that providesbetter signal quality than the currently selected cell. Such a processis called cell reselection. In general, a basic object of the cellreselection process is to select a cell that provides UE with the bestquality from a viewpoint of the quality of a radio signal.

In addition to the viewpoint of the quality of a radio signal, a networkmay determine priority corresponding to each frequency, and may informthe UE of the determined priorities. The UE that has received thepriorities preferentially takes into consideration the priorities in acell reselection process compared to a radio signal quality criterion.

As described above, there is a method of selecting or reselecting a cellaccording to the signal characteristics of a wireless environment. Inselecting a cell for reselection when a cell is reselected, thefollowing cell reselection methods may be present according to the RATand frequency characteristics of the cell.

-   -   Intra-frequency cell reselection: UE reselects a cell having the        same center frequency as that of RAT, such as a cell on which        the UE camps on.    -   Inter-frequency cell reselection: UE reselects a cell having a        different center frequency from that of RAT, such as a cell on        which the UE camps on    -   Inter-RAT cell reselection: UE reselects a cell that uses RAT        different from RAT on which the UE camps

The principle of a cell reselection process is as follows.

First, UE measures the quality of a serving cell and neighbor cells forcell reselection.

Second, cell reselection is performed based on a cell reselectioncriterion. The cell reselection criterion has the followingcharacteristics in relation to the measurements of a serving cell andneighbor cells.

Intra-frequency cell reselection is basically based on ranking. Rankingis a task for defining a criterion value for evaluating cell reselectionand numbering cells using criterion values according to the size of thecriterion values. A cell having the best criterion is commonly calledthe best-ranked cell. The cell criterion value is based on the value ofa corresponding cell measured by UE, and may be a value to which afrequency offset or cell offset has been applied, if necessary.

Inter-frequency cell reselection is based on frequency priority providedby a network. UE attempts to camp on a frequency having the highestfrequency priority. A network may provide frequency priority that willbe applied by UEs within a cell in common through broadcastingsignaling, or may provide frequency-specific priority to each UE throughUE-dedicated signaling. A cell reselection priority provided throughbroadcast signaling may refer to a common priority. A cell reselectionpriority for each terminal set by a network may refer to a dedicatedpriority. If receiving the dedicated priority, the terminal may receivea valid time associated with the dedicated priority together. Ifreceiving the dedicated priority, the terminal starts a validity timerset as the received valid time together therewith. While the valid timeris operated, the terminal applies the dedicated priority in the RRC idlemode. If the valid timer is expired, the terminal discards the dedicatedpriority and again applies the common priority.

For the inter-frequency cell reselection, a network may provide UE witha parameter (e.g., a frequency-specific offset) used in cell reselectionfor each frequency.

For the intra-frequency cell reselection or the inter-frequency cellreselection, a network may provide UE with a Neighboring Cell List (NCL)used in cell reselection. The NCL includes a cell-specific parameter(e.g., a cell-specific offset) used in cell reselection.

For the intra-frequency or inter-frequency cell reselection, a networkmay provide UE with a cell reselection black list used in cellreselection. The UE does not perform cell reselection on a cell includedin the black list.

Ranking performed in a cell reselection evaluation process is describedbelow.

A ranking criterion used to apply priority to a cell is defined as inEquation 1.

R _(s) =Q _(meas,s) +Q _(hyst) ,R _(n) =Q _(meas,s) −Q _(offset)  [Equation 1]

In this case, R_(s) is the ranking criterion of a serving cell, R_(n) isthe ranking criterion of a neighbor cell, Q_(meas,s) is the qualityvalue of the serving cell measured by UE, Q_(meas,n) is the qualityvalue of the neighbor cell measured by UE, Q_(hyst) is the hysteresisvalue for ranking, and Q_(offset) is an offset between the two cells.

In Intra-frequency, if UE receives an offset “Q_(offsets,n)” between aserving cell and a neighbor cell, Q_(offset)=Q_(offsets,n). If UE doesnot receive Q_(offsets,n), Q_(offset)=0.

In Inter-frequency, if UE receives an offset “Q_(offsets,n)” for acorresponding cell, Q_(offset)=Q_(offsets,n)+Q_(frequency). If UE doesnot receive “Q_(offsets,n)”, Q_(offset)=Q_(frequency).

If the ranking criterion R_(s) of a serving cell and the rankingcriterion R_(n) of a neighbor cell are changed in a similar state,ranking priority is frequency changed as a result of the change, and UEmay alternately reselect the twos. Q_(hyst) is a parameter that giveshysteresis to cell reselection so that UE is prevented from toalternately reselecting two cells.

UE measures R_(s) of a serving cell and R_(n), of a neighbor cellaccording to the above equation, considers a cell having the greatestranking criterion value to be the highest-ranked cell, and reselects thecell.

In accordance with the criterion, it may be checked that the quality ofa cell is the most important criterion in cell reselection. If areselected cell is not a suitable cell, UE excludes a correspondingfrequency or a corresponding cell from the subject of cell reselection.

In order to perform the cell reselection according to the cellreselection estimation, when the cell reselection reference is satisfiedfor a specific time, the terminal determines that the cell reselectionreference is satisfied and may perform cell movement to a selectedtarget cell. In this case, the specific time may be given from thenetwork as a Treselection parameter. The Treselection may specify a cellreselection timer value, and may be defined with respect to eachfrequency of the E-UTRAN and other RAT.

Hereinafter, cell reselection information used for cell reselection ofthe terminal will be described.

The cell reselection information is a type of a cell reselectionparameter and may be transmitted and provided to the terminal whilebeing included in the system information broadcasted from the network.The cell reselection parameter provided to the terminal may includefollowing types.

Cell reselection priority cellReselectionPriority: ThecellReselectionPriority parameter specifies a priority with respect to afrequency of the E-UTRAN, a frequency of a UTRAN, a group of GERANfrequencies, a band glass of a CDMA2000 HRPD or a band glass of aCDMA2000 1xRTT.

Qoffset_(s,n): specifies an offset value between two cells.

Qoffset_(frequency): specifies frequency specific offset with respect toan E-UTRAN frequency having the same priority.

Q_(hyst): specifies a hysteresis value with respect a rank index.

Q_(qualmin): specifies a required minimum quality level in a dB unit.

Q_(rxlevmin): specifies a required minimum Rx in a dB unit.

Treselection_(EUTRA): may specify a cell reselection timer value for theE-UTRAN, and may be configured with respect to each frequency of theE-UTRAN.

Treselection_(UTRAN): specifies a cell reselection timer value for theUTRAN.

Treselection_(GERA): specifies a cell reselection timer value for theGERAN.

Treselection_(CDMA) _(—) _(HRPD): specifies a cell reselection timervalue for CDMA HRPD.

Treselection_(CDMA) _(—) _(1xRTT): specifies a cell reselection timervalue for CDMA 1xRTT.

Thresh_(x, HighP): specifies a Srxlev threshold value used by a terminalupon cell reselection to an RAT/frequency having a priority higher thana serving frequency. A specific threshold value may be independentlyconfigured with respect to each frequency of the E-UTRAN and the UTRAN,each group of a GERAN frequency, each band glass of CDMA2000 HRPD andeach band glass of CDMA2000 1xRTT.

Thresh_(x, HighQ): When cell reselection to RAT/frequency having apriority higher than the serving frequency is performed, a Squalthreshold value used by a terminal is specified in a dB unit. Thespecific threshold value may be independently configured with respect toeach frequency of the E-UTRAN and a UTRAN FDD.

Thresh_(x, LowP): When cell reselection to RAT/frequency having apriority lower than the serving frequency is performed, a Srxlevthreshold value used by a terminal is specified in a dB unit. Thespecific threshold value may be independently configured with respect toeach frequency of the E-UTRAN and a UTRAN FDD, each group of a GERANfrequency, each band glass of a CDMA2000 HRPD and each band glass ofCDMA2000 1xRTT.

Thresh_(x, LowQ): When cell reselection to RAT/frequency having apriority lower than the serving frequency is performed, a Squalthreshold value used by a terminal is specified in a dB unit. Thespecific threshold value may be independently configured with respect toeach frequency of the E-UTRAN and a UTRAN FDD.

Thresh_(Serving, LowP): When cell reselection to RAT/frequency having apriority lower than the serving frequency is performed, a Srxlevthreshold value used by a terminal is specified in a dB unit.

Thresh_(Serving, LowQ): When cell reselection to RAT/frequency having apriority lower than the serving frequency is performed, a Squalthreshold value used by a terminal is specified in a dB unit.

S_(IntraSearchP): specifies a Srxlev threshold value with respect tointra-frequency measurement in a dB unit.

S_(IntraSearchQ): specifies a Squal threshold value with respect tointra-frequency measurement in a dB unit.

S_(nonIntraSerachP): specifies E-UTRAN inter-frequency and a Srxlevthreshold value with respect to inter-RAT measurement.

S_(nonIntraSearchQ): specifies E-UTRAN inter-frequency and a Squalthreshold value with respect to E-UTRAN inter-frequency and inter-RATmeasurement.

Meanwhile, the cell reselection information may be provided while beingincluded in a RRC connection release message which is a RRC messagetransmitted for RRC connection release between the network and theterminal. For example, the RRC connection release message may include asub-carrier frequency list and cell reselection priority of the E-UTRAN,a sub-carrier frequency list and cell reselection priority of theUTRA-FDD, a sub-carrier frequency list and cell reselection priority ofthe UTRA-TDD, a sub-carrier frequency list and cell reselection priorityof the GERAN, a band glass list and cell reselection priority of theCDMA2000 HRPD, and a band glass list and cell reselection priority ofCDMA2000 1xRTT.

Hereinafter, radio link monitoring (RLM) will be described.

The terminal monitors downlink quality based on a cell-specificreference signal in order to detect downlink radio link quality of aPCell. The terminal estimates the downlink radio link quality for thepurpose of monitoring downlink radio link quality of the PCell andcompares the estimated downlink radio link quality with threshold valuesQout and Qin. The threshold values Qout is defined as a level at which adownlink radio link may not be received, which corresponds to a 10%block error rate of hypothetical PDCCH transmission by taking intoconsideration a PDFICH error. The threshold value Qin is defined as adownlink radio link quality level which may be stable more than a levelof the threshold value Qout, which corresponds to a 2% block error rateof hypothetical PDCCH transmission by taking into consideration thePCFICH error.

A Radio Link Failure (RLF) is described below.

UE continues to perform measurements in order to maintain the quality ofa radio link with a serving cell from which the UE receives service. TheUE determines whether or not communication is impossible in a currentsituation due to the deterioration of the quality of the radio link withthe serving cell. If communication is almost impossible because thequality of the serving cell is too low, the UE determines the currentsituation to be an RLF.

If the RLF is determined, the UE abandons maintaining communication withthe current serving cell, selects a new cell through cell selection (orcell reselection) procedure, and attempts RRC connectionre-establishment with the new cell.

In the specification of 3GPP LTE, the following examples are taken ascases where normal communication is impossible.

-   -   A case where UE determines that there is a serious problem in        the quality of a downlink communication link (a case where the        quality of a PCell is determined to be low while performing RLM)        based on the radio quality measured results of the PHY layer of        the UE    -   A case where uplink transmission is problematic because a random        access procedure continues to fail in the MAC sublayer.    -   A case where uplink transmission is problematic because uplink        data transmission continues to fail in the RLC sublayer.    -   A case where handover is determined to have failed.    -   A case where a message received by UE does not pass through an        integrity check.

An RRC connection re-establishment procedure is described in more detailbelow.

FIG. 7 is a diagram illustrating an RRC connection re-establishmentprocedure.

Referring to FIG. 7, UE stops using all the radio bearers that have beenconfigured other than a Signaling Radio Bearer (SRB) #0, and initializesa variety of kinds of sublayers of an Access Stratum (AS) (S710).Furthermore, the UE configures each sublayer and the PHY layer as adefault configuration. In this process, the UE maintains the RRCconnection state.

The UE performs a cell selection procedure for performing an RRCconnection reconfiguration procedure (S720). The cell selectionprocedure of the RRC connection re-establishment procedure may beperformed in the same manner as the cell selection procedure that isperformed by the UE in the RRC idle state, although the UE maintains theRRC connection state.

After performing the cell selection procedure, the UE determines whetheror not a corresponding cell is a suitable cell by checking the systeminformation of the corresponding cell (S730). If the selected cell isdetermined to be a suitable E-UTRAN cell, the UE sends an RRC connectionre-establishment request message to the corresponding cell (S740).

Meanwhile, if the selected cell is determined to be a cell that uses RATdifferent from that of the E-UTRAN through the cell selection procedurefor performing the RRC connection re-establishment procedure, the UEstops the RRC connection re-establishment procedure and enters the RRCidle state (S750).

The UE may be implemented to finish checking whether the selected cellis a suitable cell through the cell selection procedure and thereception of the system information of the selected cell. To this end,the UE may drive a timer when the RRC connection re-establishmentprocedure is started. The timer may be stopped if it is determined thatthe UE has selected a suitable cell. If the timer expires, the UE mayconsider that the RRC connection re-establishment procedure has failed,and may enter the RRC idle state. Such a timer is hereinafter called anRLF timer. In LTE spec TS 36.331, a timer named “T311” may be used as anRLF timer. The UE may obtain the set value of the timer from the systeminformation of the serving cell.

If an RRC connection re-establishment request message is received fromthe UE and the request is accepted, a cell sends an RRC connectionre-establishment message to the UE.

The UE that has received the RRC connection re-establishment messagefrom the cell reconfigures a PDCP sublayer and an RLC sublayer with anSRB1. Furthermore, the UE calculates various key values related tosecurity setting, and reconfigures a PDCP sublayer responsible forsecurity as the newly calculated security key values. Accordingly, theSRB 1 between the UE and the cell is open, and the UE and the cell mayexchange RRC control messages. The UE completes the restart of the SRB1,and sends an RRC connection re-establishment complete message indicativeof that the RRC connection re-establishment procedure has been completedto the cell (S760).

In contrast, if the RRC connection re-establishment request message isreceived from the UE and the request is not accepted, the cell sends anRRC connection re-establishment reject message to the UE.

If the RRC connection re-establishment procedure is successfullyperformed, the cell and the UE perform an RRC connection reconfigurationprocedure. Accordingly, the UE recovers the state prior to the executionof the RRC connection re-establishment procedure, and the continuity ofservice is guaranteed to the upmost.

FIG. 8 is a flowchart illustrating a measuring method according to therelated art.

The terminal receives measurement configuration information from a basestation (S810). A message including measurement configurationinformation refers to a measurement configuration message. The terminalperforms measurement based on the measurement configuration information(S820). If the measurement result satisfies a report condition in themeasurement configuration information, the terminal reports themeasurement result to the base station. A message including themeasurement result refers to a measurement report message.

The measurement configuration information may include followinginformation.

(1) Measurement object information: represents information on an objectto be measured by the terminal. The measurement object includes at leastone of an intra-frequency measurement object being a measurement objectin a cell, an inter-frequency measurement object being a measurementobject between cells, and an inter-RAT measurement object being aninter-RAT measurement object. For example, the inter-frequencymeasurement object may indicate a neighboring cell having the samefrequency band as that of the serving cell, the inter-frequencymeasurement object may indicate a neighboring cell having a frequencyband different from that of the serving cell, and an inter-RATmeasurement object may indicate a neighboring cell of a RAT differentfrom that of the serving cell.

(2) Reporting configuration information: represents information on areporting condition and a reporting type when transmission of themeasurement result is reported. The reporting configuration informationmay be configured as a list of reporting configuration. Each reportingconfiguration may include a reporting criterion and a reporting format.The reporting criterion is a criterion triggering transmission of themeasurement result by the terminal. The reporting criterion may includea period of a measurement reporting or a single event for themeasurement reporting. The reporting format is information on which typethe terminal configures the measurement result.

(3) Measurement identity information: represents information on ameasurement identity to determine when the terminal reports a certainmeasurement object as a certain type by associating the measuringreporting with reporting configuration. The measurement identityinformation is included in the measurement reporting message, which mayrepresent which measurement object is the measurement result and inwhich reporting condition the measurement reporting is generated.

(4) Quantity configuration information: represents information on aparameter for configuring filtering of a measurement unit, a reportingunit, and/or a measurement result value.

(5) Measurement gap information: represents information on a measurementgap which is an interval when the terminal may use for measurementwithout considering data transmission with the serving cell becausedownlink transmission or uplink transmission is not scheduled.

The terminal has a measurement object list, a measurement reportingconfiguration list, and a measurement identity list in order to performa measurement procedure.

In the 3GPP LTE, the base station may configure only one measurementobject with respect to one frequency band to the terminal. According tosection 5.5.4 of 3GPP TS 36.331 V8.5.0 (2009-03) “Evolved UniversalTerrestrial Radio Access (E-UTRA) Radio Resource Control (RRC); Protocolspecification (Release 8)”, events resulting in the measurementreporting as listed in a following table 2 are defined.

TABLE 2 Event Reporting condition Event A1 Serving becomes better thanthreshold Event A2 Serving becomes worse than threshold Event A3Neighbour becomes offset better than serving Event A4 Neighbour becomesbetter than threshold Event A5 Serving becomes worse than threshold1 andneighbour becomes better than threshold2 Event B1 Inter RAT neighbourbecomes better than threshold Event B2 Serving becomes worse thanthreshold1 and inter RAT neighbour becomes better than threshold2

If the measurement result of the terminal satisfies the configuredevent, the terminal transmits a measurement reporting message to thebase station.

FIG. 9 illustrates an example of measurement configuration in theterminal.

First, the measurement identity 1 ( 901) connects an intra-frequencymeasurement object with a reporting configuration 1. The terminalperforms intra frequency measurement, and the reporting configuration 1is used to determine criterion and type of the measurement resultreporting.

As in the measurement identity 1 ( 901), the measurement identity 2 (902) is connected to the intra-frequency measurement object, butconnects the intra-frequency measurement object to the reportingconfiguration 2. The terminal performs measurement and the reportingconfiguration 2 is used to determine criterion and type of themeasurement result reporting.

According to a measurement identity 1 ( 901) and a measurement identity2 ( 902), even if a measurement result with respect to theintra-frequency measurement object satisfies one of reportingconfiguration 1 and reporting configuration 2, the terminal transmitsthe measurement result.

The measurement identity 3 ( 903) connects the inter-frequencymeasurement object 1 to the reporting configuration 3. If themeasurement result with respect to the inter-frequency measurementobject 1 satisfies a reporting condition included in the reportingconfiguration 1, the terminal reports the measurement result.

The measurement identity 4 ( 904) connects the inter-frequencymeasurement object 2 to the reporting configuration 2. If themeasurement result with respect to the inter-frequency measurementobject 2 satisfies a reporting condition included in the reportingconfiguration 2, the terminal reports the measurement result.

Meanwhile, the measurement object, reporting configuration and/ormeasurement identity may be added, changed, and/or removed. This may beindicated by sending a new measurement configuration message or themeasurement configuration change message to the terminal.

FIG. 10 illustrates an example of removing the measurement identity. Ifthe measurement identity 2 ( 902) is removed, measurement with respectto a measurement object associated with the measurement identity 2 (902) is stopped and the measurement reporting is not transmitted. Themeasurement object associated with the removed measurement identity orthe reporting configuration may not be changed.

FIG. 11 illustrates an example of removing the measurement object. Ifthe inter-frequency measurement object 1 is removed, the terminal alsoremove the measurement identity 3 ( 903) associated with theinter-frequency measurement object 1. Measurement with respect to theinter-frequency measurement object 1 is stopped and the measurementreporting is not transmitted. However, the reporting configurationassociated with the remove inter-frequency measurement object 1 may notbe changed or removed.

If the reporting configuration is removed, the terminal also removes ameasurement identity associated with the reporting configuration. Theterminal stops measurement with respect to the measurement objectassociated with the associated measurement identity. However, themeasurement object associated with the removed reporting configurationmay not be changed or removed.

The measurement reporting may include a measurement identity, measuredquality of the serving cell and a measurement result of the neighboringcell. The measurement identity identifies a measurement object to whichthe measurement report is triggered. The measurement result of theneighboring cell may include a cell identity and measured quality of theneighboring cell. The measured quality may include at least one ofReference Signal Received Power (RSRP) and Reference Signal ReceivedQuality (RSRQ).

FIG. 12 is a flowchart illustrating a method for performing a loggedMDT.

Referring to FIG. 12, UE receives a logged measurement configuration(S1210). The logged measurement configuration may be included in an RRCmessage and transmitted as a downlink control channel. The loggedmeasurement configuration may include at least one of pieces ofinformation about a TCE ID, a reference time that is a criterion inperforming logging, logging duration, a logging interval, and an areaconfiguration. The logging interval is indicative of an interval inwhich a measured result is stored. The logging duration is indicative ofduration in which UE performs a logged MDT. The reference time isindicative of the time, that is, a criterion for duration in which alogged MDT is performed. The area configuration is indicative of an areaon which UE has been requested to perform logging.

Meanwhile, the UE starts a validity timer when it receives the loggedmeasurement configuration. The validity timer means the lifetime of thelogged measurement configuration, and may be specified based oninformation about logging duration. The duration of the validity timermay also indicate the validity of a measured result owned by the UE inaddition to the valid lifetime of the logged measurement configuration.

A procedure in which the UE receives the logged measurementconfiguration and a corresponding overall procedure is performed asdescribed above is called a configuration phase.

When the UE enters an RRC idle state (S1221), the UE logs a measuredresult while the validity timer is driven (S1222). The value of themeasured result may be RSRP, RSRQ, Received Signal Code Power (RSCP), orEc/No. Information obtained by logging the measured result is called alogged measurement and/or a measured result log. A temporal phase inwhich UE logs a measured result more than once is called a loggingphase.

The execution of a logged MDT based on a logged measurementconfiguration by UE may be changed depending on a place where the UE ispresent.

FIG. 13 is a diagram illustrating an example of a logged MDT accordingto a logging area.

A network may configure a logging area, that is, an area in which UEneeds to perform logging. The logging area may be represented in theform of a cell list or may be represented in the form of a trackingarea/location area list. If a logging area has been configured for theUE, the UE stops logging when it deviates from the logging area.

Referring to FIG. 13, a first area 1310 and a third area 1330 are areasconfigured as a logging area, and a second area 1320 is an area in whichlogging is not permitted. The UE performs logging in the first area1310, but does not perform logging in the second area 1320. The UEperforms logging again when it moves from the second area 1320 to thethird area 1330.

FIG. 14 is a diagram illustrating an example of a logged MDT accordingto a change of an RAT.

UE performs logging only when it camps on an RAT through which a loggedmeasurement configuration has been received, but stops logging in otherRATs. In this case, the UE may log cell information of another RAT inaddition to the RAT in which the UE camps on.

A first area 1410 and a third area 1430 are E-UTRAN areas, and a secondarea 1420 is a UTRAN area. A logged measurement configuration isreceived from the E-UTRAN. The UE does not perform MDT measurements whenit enters the second area 1420.

Referring back to FIG. 12, if the UE enters an RRC connected state(S1231) and has logged measurements to be reported, the UE notifies aneNB that it has the logged measurements to be reported (S1232). When theUE has established RRC connection or re-established RRC connection orRRC connection is reconfigured, the UE may notify the eNB that it hasthe logged measurements. Furthermore, if the UE performs handover, itmay notify a target handover cell that it has the logged measurements.To notify, by the UE, the eNB of the logged measurements may includeincluding a logged measurement availability indicator, that is,indication information providing notification of the presence of thelogged measurements, in an RRC message transmitted from the UE to theeNB and sending the RRC message. The RRC message may be an RRCconnection establishment-complete message, an RRC connectionre-establishment-complete message, an RRC reconfiguration-completemessage, or a handover-complete message.

When the eNB receives a signal providing notification of the presence ofthe logged measurements from the UE, it requests the UE to report thelogged measurements (S1233). To request the report on the loggedmeasurements may include including a logged measurement reportingrequest parameter regarding information indicative of the loggedmeasurements in an RRC message and sending the RRC message. The RRCmessage may be a UE information request message.

When the UE receives the request for the report on the loggedmeasurements from the eNB, it reports the logged measurements to the eNB(S1234). To report the logged measurements to the eNB may includeincluding a logged measurement report, including the loggedmeasurements, in an RRC message and sending the RRC message to the eNB.The RRC message may be a UE information report message. In reporting thelogged measurements, the UE may report all of the logged measurementsowned by the UE to the eNB or some of the logged measurements owned bythe UE to the eNB at a point of time at which the report is made. Ifsome of the logged measurements owned by the UE is reported, thereported some logged measurements may be discarded.

A phase in which a process of notifying, by UE, an eNB of the presenceof logged measurements, receiving a request for a report from the eNB,and reporting the logged measurements is performed as described above iscalled a reporting phase.

While a logged MDT is performed, a subject measured by UE is chieflyrelated to a wireless environment. The MDT measurements may include acell identity and the signal quality and/or signal intensity of a cell.The MDT measurements may include a measurement time and a measurementplace. Table 3 below illustrates contents logged by UE.

TABLE 3 PARAMETER (SET) DESCRIPTION Serving cell Global cell identity ofa serving cell identity Measured result Measured Reference SignalReceived Power (RSRP) of serving cell of a serving cell MeasuredReference Signal Received Quality (RSRQ) of a serving cell Measuredresult Cell identities of measured E-UTRA cells, Measured of neighborcell result of E-UTRA cells Cell identities of measured UTRA cells,Measured result of UTRA cells Cell Identities of measured GERAN cells,Measured result of GERAN cells Cell Identities of measured CDMA 2000cells, Measured result of CDMA 2000 cells Time stamp The moment of alogging measured result, calculated as {current time minusabsoluteTimeStamp} in seconds Location Detailed location information atthe moment of logging information

Information logged at different logging points of time may be stored sothat it is divided into different log entries as follows.

FIG. 15 is a diagram illustrating an example of logged measurements.

The logged measurements include one or more log entries.

The log entry includes a logging location, a logging time, a servingcell identity, a serving measured result, and a neighbor cell measuredresult.

The logging location is indicative of a location in which UE hasperformed measurements. The logging time is indicative of the time whenUE performed measurements. Information logged on a different loggingtime is stored in a different log entry.

The serving cell identity may include a cell identity in Layer 3, whichis called a Global Cell Identity (GCI). The GCI is a set of a PhysicalCell Identity (PCI) and a PLMN identity.

Meanwhile, UE may analyze and log indices related to performance of theUE in addition to a wireless environment. For example, the indices mayinclude a throughput and an erroneous transmission/reception rate).

Referring back to FIG. 12, the aforementioned logging phase andreporting phase may be present in the logging duration in plural times(S1241, S1242).

The eNB may record/store the logged measurements in a TCE when itreceives a report on the logged measurements.

After the validity timer expires, that is, after a lapse of the loggingduration, if the UE has logged measurements that have not yet beenreported, the UE performs a procedure for reporting the loggedmeasurements to the eNB. A phase in which an overall procedure forreporting the logged measurements to the eNB is performed is called apost-reporting phase.

After the logging duration is terminated, the UE discards the loggedmeasurement configuration and starts a conservation timer. After thelogging duration is terminated, the UE stops MDT measurements. Howeveralready logged measurements remain without being discarded. Theconservation timer is indicative of the lifetime of the remaining loggedmeasurements.

If the UE enters an RRC connected state before the conservation timerexpires (S1251), the UE may report logged measurements that have not yetbeen reported to the eNB. In this case, the aforementioned proceduresfor reporting the logged measurements may be performed (S1252, S1253,and S1254). When the conservation timer expires, the remaining loggedmeasurements may be discarded. The eNB may record/store the loggedmeasurements when a report on the logged measurements is received.

The conservation timer may be fixed to a predetermined value for the UEand may be previously set in the UE. For example, the value of theconservation timer may be 48 hours. Alternatively, the value of theconservation timer may be included in a logged measurement configurationand delivered to the UE or may be included another RRC message anddelivered to the UE.

Meanwhile, when a new logged measurement configuration is transferred tothe UE, the UE may update an existing logged measurement configurationwith the newly obtained logged measurement configuration. In this case,a validity timer may be started again from the time when the loggedmeasurement configuration is newly received. Furthermore, loggedmeasurements based on a prior logged measurement configuration may bediscarded.

FIG. 16 is a diagram illustrating an example of an immediate MDT. Theimmediate MDT is based on a Radio Resource Management (RRM) measurementand report mechanism. In addition, information related to a location isadded when a measured report is made and reported to an eNB.

Referring to FIG. 16, UE receives an RRC connection reconfigurationmessage (S1610) and sends an RRC connection reconfiguration-completemessage (S1620). Accordingly, the UE enters an RRC connected state. TheUE may receive a measurement configuration by receiving the RRCconnection reconfiguration message. In the example of FIG. 16, themeasurement configuration is received through the RRC connectionreconfiguration message, but may be included in an RRC message accordingto an example and transmitted.

The UE performs measurements and evaluations in the RRC connected state(S1631) and reports a measured result to an eNB (S1632). In an immediateMDT, the measured result may provide accurate location information, ifpossible, as in an example of Global Navigation Satellite System (GNSS)location information. For location measurement, such as an RFfingerprint, neighbor cell measurement information that may be used todetermine the location of the UE may be provided.

From FIG. 16, it may be seen that even after the prior measurements andevaluations (S1631) and report (S1632), the UE reports a measured resultto the eNB (S1642) right after performing measurements and evaluations(S1641). This may be said to be the greatest difference between a loggedMDT and an immediate MDT.

A Multimedia Broadcast and Multicast Service (MBMS) is described indetail below.

A logical channel MCCH channel or MTCH channel may be mapped to atransport channel MCH channel for the MBMS. The MCCH channel sends anMBMS-related RRC message, and the MTCH channel sends traffic of aspecific MBMS service. A single MCCH channel is present in each MBMSSingle Frequency Network (MBSFN) area in which the same MBMSinformation/traffic is transmitted. If a single cell provides aplurality of MBSFN areas, UE may receive a plurality of MCCH channels.If an MBMS-related RRC message is changed in a specific MCCH channel, aPDCCH channel sends an indicator indicative of an MBMS Radio NetworkTemporary Identity (M-RNTI) and a specific MCCH channel. UE supportingthe MBMS may receive the M-RNTI and the MCCH indicator through the PDCCHchannel, may check that the MBMS-related RRC message has been changed ina specific MCCH channel, and may receive the specific MCCH channel. TheRRC message of the MCCH channel may be changed for each change cycle andrepeatedly broadcasted for each repetition cycle.

UE may also be provided with a dedicated service while it is providedwith an MBMS service. For example, a user may watch TV through an MBMSservice through his or her smart phone and simultaneously performchatting using an Instant Messaging (IM) service, such as MSN or Skype,using the smart phone. In this case, the MBMS service is providedthrough an MTCH received by several UE, and a service provided to eachUE, such as an IM service, may be provided through a dedicated bearer,such as a DCCH or DTCH.

In one area, a specific eNB may use several frequencies at the sametime. In this case, in order to efficiently use radio resources, anetwork may select one of the several frequencies, may provide an MBMSservice only the selected frequency, and may provide dedicated bearersto respective UEs in all the frequencies.

In this case, if UE provided with a service using a dedicated bearer ina frequency through which the MBMS service is not provided wants toreceive the MBMS service, the UE need to perform handover to thefrequency through which the MBMS service is provided. To this end, theUE sends an MBMS interest indication to an eNB. That is, if the UE wantsto receive the MBMS service, it sends an MBMS interest indication to theeNB. When the indication is received, the eNB recognizes that the UEwants to receive the MBMS service and moves the UE to the frequencythrough which the MBMS service is provided. In this case, the MBMSinterest indication means information indicating that the UE wants toreceive the MBMS service and additionally includes information about afrequency to which the UE wants to move.

UE that wants to receive a specific MBMS service first checks frequencyinformation and broadcasting time information through which the specificMBMS service is provided. If the MBMS service is already broadcasted orstarts to be broadcasted, the UE sets the highest priority in afrequency through which the MBMS service is provided. The UE moves to acell that provides the MBMS service by performing a cell reselectionprocedure using the reconfigured frequency priority information, andreceives the MBMS service.

If UE receives an MBMS service or is interested to receiving an MBMSservice and if UE is able to receive an MBMS service while it camps on afrequency through which the MBMS service is provided, the highestpriority may be considered to have been applied to the correspondingfrequency during an MBMS session as long as the following situationcontinues in the state in which a reselected cell broadcasts SIB13.

-   -   If the inclusion of one or more MBMS Service Area Identities        (SAIs) in the User Service Description (USD) of a corresponding        service is indicated by SIB15 of a serving cell.    -   If SIB 15 is not broadcasted within a serving cell and a        corresponding frequency is included in the USD of a        corresponding service.

The aforementioned MDT may be applied in relation to an MBMS. A networkmay enable specific UE to report information related to an MBMS to thenetwork. A series of procedures, including a corresponding configurationfrom a network and/or an UE MBMS information reporting operation, may beimplemented as in the aforementioned MDT, which may be called an MBMSMDT.

A network may select UE for an MBMS MDT based on the capabilities of theUE and/or the consent of a user. However, an MBMS service is broadcastedand provided on an MBSFN area, and UE provided with the MBMS servicedoes not provide corresponding feedback. Accordingly, the network rarelychecks the MBMS reception status of the UE. Accordingly, the network mayperform a configuration in UE so that MBMS MDT management is performedregardless of the MBMS reception status of the UE.

When UE measures MBMS transmission related to an MBMS service that isnot interested, the UE consumes power for the purpose of the reportingof MBMS information. If the reporting of MBMS information depends on theimprovement of MBMS service reception from a viewpoint of a user,excessive consumption of UE-side power attributable to the improvementmay not be preferred. Accordingly, a method capable of improving MBMSservice reception for UE while preventing excessive consumption ofUE-side power needs to be proposed.

FIG. 17 is a diagram illustrating a method for reporting MBMSinformation in accordance with an embodiment of the present invention.

Referring to FIG. 17, UE receives an MBMS reporting configuration from anetwork (S1710). The MBMS reporting configuration may includeconfiguration information for obtaining, logging, and reportinginformation related to the MBMS service reception of the UE. Theconfiguration information set in the UE through the MBMS reportingconfiguration may be implemented as follows.

(1) The MBMS reporting configuration may include MBMS logging executioninformation. The MBMS logging execution information may be informationspecifying that the UE will obtain and log MBMS information when andhow. The MBMS logging execution information may include the followinglower information.

-   -   A logging execution condition: the logging execution condition        specifies a condition in which UE determines to execute the        acquisition and logging of MSBM information. The UE may        determine to execute the acquisition and logging of MSBM        information depending on the logging execution condition.        Furthermore, the UE may determine to stop the acquisition and        logging of MSBM information depending on the logging execution        condition. The following conditions may be taken into        consideration as the logging execution condition.

a) An MSBM service reception failure

b) The deterioration of MSBM service reception quality

c) The failure of a measured result of an MSBM service-specificreference signal

If the logging execution condition is included in MBMS logging executioninformation, UE may determine whether or not to execute MBMS logging byapplying the logging execution condition.

-   -   Logging duration: the logging duration indicates duration in        which UE that has determined to perform the acquisition/logging        of MBMS information obtains and logs the MBMS information. A        point of time at which logging duration starts may be a point of        time at which an MBMS reporting configuration is received or a        point of time at which the acquisition/logging of MBMS        information are first started.    -   A logging interval: the logging interval indicates a time        interval in which UE performs the acquisition/logging of MBMS        information during logging duration. If information indicative        of a logging interval is included in MBMS logging execution        information, UE may periodically perform the acquisition/logging        of MBMS information at the logging interval during logging        duration.

(2) An MBMS reporting configuration may include MBMS logging purposeinformation. The MBMS logging purpose information may indicate that anoperation according to an MBMS reporting configuration is for MBMSinformation reporting. That is, the MBMS logging purpose information mayindicate that the operation according to the MBMS reportingconfiguration is for an MBMS MDT.

A reporting configuration transmitted to UE may include MBMS loggingpurpose information indicative of an object of logging. The MBMS loggingpurpose information may indicate the report of MBMS information by UE.The logging purpose information may indicate an MBMS MDT.

(3) An MBMS reporting configuration may include MBMS logging areainformation indicative of an area in which the acquisition and loggingof MBMS information by UE is permitted. The MBMS logging areainformation may include the following information.

-   -   An MBSFN area: an MBSFN area in which the acquisition and        logging of MBMS information by UE is permitted    -   A PLMN list: a PLMN identity set in which the acquisition and        logging of MBMS information by UE is permitted

(4) An MBMS reporting configuration may include MBMS logging targetinformation specifying MBMS information to be obtained and logged by UE.The MBMS logging target information may specify the content of MBMSinformation to be obtained by UE through measurements.

(5) An MBMS reporting configuration may include MBMS reporting conditioninformation indicative of a reporting condition on logged MBMSinformation. The MBMS reporting condition information may specify thatlogged MBMS information is to be reported when, where and/or how. TheMBMS reporting condition may include the following information.

-   -   A reporting cycle: The reporting cycle of logged MBMS        information    -   A reporting event: an event that triggers the reporting of        logged MBMS information (e.g., an MBMS service failure, MBMS        service deterioration, and an RRC connected state)    -   A reporting method: The reporting of MSBM information indicates        whether one or more pieces of MSBM information, such as a logged        MDT, are logged and reported once or are immediately reported        right when the MSBM information is obtained.

(6) An MBMS reporting configuration may further include a traceparameter. The trace parameter may include at least one of a tracereference parameter, a trace recording session reference, and a TCE ID.

An MBMS reporting configuration may be provided to UE through broadcastsignaling (e.g., signaling through a BCCH and/or an MCCH). UE mayreceive an MBMS reporting configuration provided through broadcastsignaling and determine whether there is user consent for reporting MBMSinformation according to the MBMS reporting configuration. If there isuser consent, the UE may determine to apply the MBMS reportingconfiguration. If there is no user consent, the UE disregards thereceived MBMS reporting configuration. In this case, the user consentfor performing MBMS information reporting may be previously set in theUE or may be set by an application using Open Mobile Alliance (OMA)Device Management (DM), for example.

An MBMS reporting configuration may be provided to UE through dedicatedsignaling (e.g., signaling through a DCCH). An RRC message for an MBMSreporting configuration may be newly defined. Alternatively, an MBMSreporting configuration may be additionally included in an existing RRCmessage. For example, an MBMS reporting configuration may beadditionally included in a logged measurement configuration message. Ifa logged measurement configuration is used through a logged measurementconfiguration message, the logged measurement configuration message mayneed to indicate whether UE needs to perform MBMS information reports.To this end, the aforementioned MBMS logging purpose information may beincluded in the logged measurement configuration message. Meanwhile, ifa logged measurement configuration message is used for only MBMSinformation reporting, the logged measurement configuration message mayfurther include information indicating that measurement logging for alogged MDT must be omitted.

The UE determines whether or not to execute the logging of the MBMSinformation (S1720). The determination of whether or not to execute thelogging of the MBMS information by the UE may be based on a loggingexecution condition configured in the UE. The logging executioncondition to be applied by the UE, as described above, may be includedin an MBMS reporting configuration and configured in the UE or may havebeen previously configured in the UE. The UE may determine whether thelogging execution condition is satisfied and determine whether or not toexecute the logging of the MBMS information.

(1) Determine whether or not to execute the logging of the MBMSinformation depending on an MBMS service reception failure

The UE detects that an MBMS service reception failure has occurred andthus may determine to obtain and log the MBMS information. Theoccurrence of the MBMS service reception failure may be taken intoconsideration as follows.

a) If the UE does not obtain an MCCH from the cell of a frequencyprovided by an interested MBMS service, the UE may determine that theMBMS service reception failure has been detected.

b) If the UE has failed in obtaining SIB13 (if the UE has failed inobtaining the configuration of an MCCH), the UE may determine the MBMSservice reception failure has been detected.

c) If the UE has failed in obtaining SIB15S, the UE may determine thatthe MBMS service reception failure has been detected.

d) Whether the UE will detect the occurrence of the MBMS servicereception failure by applying which one of the aforementioned MBMSservice reception failure determination criteria may be previously setin the UE or may be configured in the UE through the explicit signalingof a network.

If the UE determines that the MBMS service reception failure has beensolved, the UE may determine to stop the acquisition and logging of theMBMS information. The solving of the MBMS service reception failure maybe configured contrary to the aforementioned determination criteria.

(2) Determine whether or not to execute the logging of the MBMSinformation depending on the deterioration of MBMS service receptionquality

The UE detects the deterioration of MBMS service reception quality andthus may determine to obtain and log the MBMS information. Theoccurrence of the deterioration of the MBMS service reception qualitymay be taken into consideration as follows.

a) If the block error rate (BLER) of a received MBMS service is higherthan a specific threshold, the UE may determine that the deteriorationof the MBMS service reception quality has been detected.

b) The BLER may be the CRC failure rate of transmission that includes anMBMS service and that is received by the UE in a subframe on a PMCHand/or an MTCH.

c) The BLER may be measured or evaluated as a BLER per MCS.

d) The BLER may be defined as an average BLER during a moving timewindow.

If the UE determines that the deterioration of the MBMS servicereception quality has been solved, the UE may determine to stop theacquisition and logging of the MBMS information. The solving of thedeterioration of the MBMS service reception quality may be configuredcontrary to the aforementioned determination criteria.

(3) Determine whether or not to execute the logging of the MBMSinformation depending on the failure of a measurement result of an MBMSservice-specific reference signal

The UE detects that a measurement result of an MBMS service-specificreference signal is poor and thus may determine to obtain and log theMBMS information. The occurrence of the failure of a measurement resultof the MBMS service-specific reference signal may be taken intoconsideration as follows.

a) If the measurement result of the MBMS service-specific referencesignal is lower than a specific threshold, the UE may determine that ithas detected that measurement result of the MBMS service-specificreference signal is poor.

b) The measurement result of the MBMS service-specific reference signalmay be measured and evaluated in such a manner that the UE measures asubframe on a PMCH or an MTCH that includes an MBMS service. The MBMSservice-specific reference signal may be a reference signal transmittedon an MBSFN subframe provided by the MBMS service.

c) The measurement result may be the signal intensity of the referencesignal and/or signal quality.

d) The measurement result may be defined as an average value during amoving time window.

If the UE determines that the failure of the measurement result of theMBMS service-specific reference signal has been solved, the UE maydetermine to stop the acquisition and logging of the MBMS information.The solving of the failure of the measurement result may be configuredcontrary to the aforementioned determination criteria.

One or more of the aforementioned criteria for determining whether ornot to execute the acquisition and logging of the MBMS information maybe combined and implemented. For example, one or more logging executioncriteria may be included in MBMS logging execution information so thatUE determines whether or not to execute the acquisition and logging ofthe MBMS information by taking the one or more logging executioncriteria into consideration.

The UE executes the acquisition and logging of the MBMS information(S1730). The UE may perform MBMS measurements in order to obtain theMBMS information. The UE may perform MBMS measurements on a frequencyand/or subframe provided by the MBMS service and may obtain ameasurement result. The UE may include the measurement result of theMBMS service in the MBMS information. The UE may include informationabout the location of the UE in the MBMS information when obtaining andlogging the MBMS information.

The acquisition and logging of the MBMS information by the UE may beperiodically performed when the logging execution condition issatisfied. To this end, an MBMS logging cycle may be set in the UE. TheMBMS logging cycle may be configured in the UE through the logginginterval of MBMS logging execution information of an MBMS reportingconfiguration. The UE may obtain MBMS information at a logging point oftime based on the MBMS logging cycle and may log the MBMS information.In order to periodically log the MBMS information, a timer may be set.The timer may be set as an MBMS logging cycle value. When the timerexpires, it is restarted. The UE may obtain and log MBMS informationwhen the timer expires.

The logging of the periodic MBMS information by the UE may be performedfor duration in which a logging execution condition is satisfied. If thelogging execution condition is no longer satisfied, the UE may stop theacquisition and logging of the MBMS information. If the loggingexecution condition continues to be satisfied, the logging of theperiodic MBMS information by the UE may be performed for the loggingduration. If the logging duration expires, the logging of the periodicMBMS information may be stopped.

Unlike in the logging of periodic MBMS information, the UE may obtainand log MBMS information depending on the satisfaction/dissatisfactionof the logging execution condition. That is, the UE may obtain and logthe MBMS information when the logging execution condition is satisfiedand may obtain and log MBMS information again when the logging executioncondition that has been satisfied is no longer satisfied.

Whether the UE will obtain and log the MBMS information based on whichone of the two methods may be determined by the configuration of anetwork. For example, separate information indicative of a method ofobtaining and logging MBMS information by the UE may be provided by anetwork. For another example, if logging interval information is notincluded in an MBMS reporting configuration, the UE may log MBMSinformation when a logging execution condition is satisfied and is nolonger satisfied. In contrast, if logging interval information isincluded in an MBMS reporting configuration, the UE may periodically logMBMS information for an interval in which a logging execution conditionis satisfied. If information indicative of a method of obtaining andlogging MBMS information is included in an MBMS reporting configuration,the UE may perform the acquisition and logging of MBMS informationaccording to an instructed method.

Alternatively, whether the UE will obtain and log the MBMS informationbased on which one of the two methods may have been previouslyconfigured in the UE.

The MBMS information obtained and logged by the UE may include thefollowing information. If obtained MBMS information is logged andreported to a network at once without immediately reporting the obtainedMBMS information, a piece of the logged MBMS information may be storedas a single logged entry.

(1) MBMS control information

-   -   MBMS service area information about the interest MBMS service of        UE or an MBMS service being received by the UE (e.g., MBMS SAD    -   MBSFN area information about the interest MBMS service of UE or        an MBMS service being received by the UE (MBSFN area identity)    -   PMCH information related to each MBSFN area of the interest MBMS        service of UE or an MBMS service being received by the UE    -   A Temporary Mobile Group Identity (TMGI) for the interest MBMS        service of UE or an MBMS service being received by the UE    -   MBSFN subframe information (MBSFN-SubframeConfig)

(2) MBMS cell information

-   -   An MBMS cell means a cell which provides the interest MBMS        service of UE on the frequency of the corresponding cell. The        MBMS cell may have a different meaning from a serving cell on        another frequency.    -   The MBMS cell information may include an MBMS cell ID list. If a        serving cell is different from an MBMS cell, the ID of a        corresponding cell may be logged. If the frequency of a serving        cell is different from the frequency of an MBMS cell, the ID of        a corresponding cell may be logged.    -   The MBMS cell information may include an frequency list of an        MBMS cell which provides the interest MBMS service of UE or an        MBMS service being received by the UE.    -   The MBMS cell information may include the PLMN of an MBMS cell.        The PLMN of an MBMS cell may be included in MBMS cell        information if the PLNM of a corresponding MBMS cell is        different from the rPLMN of UE.    -   An indicator indicating that UE currently camps on an MBMS        frequency or indicating whether the MBMS frequency is the same        as the frequency of a serving cell with which the UE has        established RRC connection may be included in the MBMS cell        information.

(3) Logging reason information

-   -   The logging reason information may be indicative of the logging        reason of MBMS information logged by UE. The logging reason        information may indicate that the logged MBMS information is        based on periodic logging. The logging reason information may        indicate whether the logged MBMS information is based on        specific event-based logging, such as a logging execution        condition. The logging reason information may be included in        each log entry as unit MBMS information logged at a specific        point of time and may be configured to indicate a reason for        which the corresponding log entry has been logged. The logging        reason information may be configured to indicate a reason for        which all pieces of MBMS information logged at a plurality of        points of time, that is, a plurality of log entries has been        logged.

(4) MBMS service deterioration/failure reason information

-   -   The MBMS service deterioration/failure reason information may be        indicative of an MBMS service failure. An MCCH acquisition        failure, an MBMS service reception failure from a cell on a        frequency for the interest MBMS service of UE, an SIB 13        acquisition failure (MCCH configuration acquisition failure), an        SIB 15 acquisition failure, entry into a cell that does not        provide an MBMS service (e.g., entry into a CSG cell/cell in        which an MBSFN subframe has not been configured/irregular        cell/invalid cell/entry into a cell of a PLMN other than an        rPLMN), and deviation from a regular camp state may be taken        into consideration as the MBMS service failure.    -   The MBMS service deterioration/failure reason information may be        indicative of the deterioration of MBMS service reception        quality. The MBMS service deterioration/failure reason        information may be indicative of a reason that has caused the        deterioration of MBMS service reception quality.

(5) MBMS service reception quality of information

-   -   A Block Error Rate (BLER) per Modulation and Coding Scheme (MCS)    -   A BLER per MCS in each MBSFN area    -   If an MBMS-specific reference signal is to be measured, a        measured result (RSRP, RSRQ) of a serving cell

(6) MBMS transmission information

-   -   An MCS applied to an MCCH    -   An MCS applied to a PMCH

(7) Wireless measurements information

-   -   Serving cell information (a PCI, a GCI, a serving frequency, a        tracking area, a PLMN list, etc.)    -   If a common reference signal has been measured, a measured        result (RSRP, RSRQ) of a serving cell    -   Neighbor cell information (a PCI, a neighbor cell frequency)    -   A measured result (RSRP, RSRQ) of a neighbor cell

(8) Time information

-   -   Logging time information (e.g., SS:MM:HH:DD)    -   Service deterioration time    -   A point of time at which the deterioration of service quality        occurred    -   A point of time at which the deterioration of service quality        was previously generated    -   Service deterioration the duration    -   An MBMS service deterioration occurrence indicator    -   An indicator per log entry

(9) Information about the location of UE at a point of time at whichMBMS information is logged (e.g., GPS, GNSS-based location information)

The MBMS information that may be logged by the UE may be obtained and/ordetermined from a serving cell and/or a non-serving cell.

The UE reports the logged MBMS information to the network (S1740).

To report, by the UE, the logged MBMS information to the network may beperformed as in an existing logged MDT. The UE may include a logged MBMSinformation availability indicator, indicating that there is logged MBMSinformation to be reported, in an RRC connection establishment-completemessage, an RRC connection reconfiguration-complete message, or an RRCconnection re-establishment-complete message, and send the message.

When the reporting of the logged MBMS information is requested by thenetwork, the UE may report the logged MBMS information to the network ata specific report time interval during an RRC connected state. Thespecific report time interval may be set by the network.

The reporting of logged MBMS information by UE may be performed withrespect to a network after MBMS measurements are obtained and/or rightafter the logged MBMS information is obtained. UE may immediately reportMBMS information to a network without a request for the report by thenetwork. In accordance with the method of immediately reporting MBMSinformation as described above, a logging execution condition may betaken into consideration as a condition in which the acquisition andreporting of the MBMS information are triggered. UE in a logging RRCconnected state may report MBMS information to a network right after theMBMS information is obtained. UE in an RRC connected state may includeMBMS information in an RRC connection establishment-complete message,RRC connection re-establishment-complete message, or a separate RRCmessage after the RRC connected state is established and send themessage to a network.

How UE will report MBMS information may be performed depending on areporting method previously configured in the UE. Alternatively, ifinformation indicative of a reporting method is included in an MBMSreporting configuration, UE may report MBMS information depending onreporting method indication information included in the MBMS reportingconfiguration.

A detailed example of a method of reporting MBMS information inaccordance with an embodiment of the present invention is described indetail with reference to a figure.

FIG. 18 is a diagram illustrating an example of a method of reportingMBMS information in accordance with an embodiment of the presentinvention.

Referring to FIG. 18, an LTE cell is assumed to be an MBMS cellproviding UE with an interested MBMS service.

The UE receives an MBMS reporting configuration from the LTE cell(S1810). The MBMS reporting configuration may include a loggingexecution condition, logging duration T_(D), and a logging interval T₁as MBMS logging execution information. The logging execution conditionmay indicate an MBMS service reception failure.

The LTE cell is an MBMS cell which provides the UE with an interestedMBMS service, and thus the UE may receive an MBMS service from the LTEcell. While the UE receives the MBMS service, the reception failure ofthe MBMS service may occur (S1821). In this case, the UE determines tostart the logging of MBMS information and logs related MBMS information(S1822). The UE performs MBMS measurements in order to obtain the MBMSinformation. The UE may perform wireless measurements on a frequencyand/or subframe provided by the MBMS service. The UE may include ameasurement result in the MBMS information. Furthermore, the UE mayinclude location information indicative of the location of the UE in theMBMS information at a point of time at which the MBMS information isobtained and logged.

Furthermore, the UE may include logging reason information indicative ofa reason for which the MBMS information has been obtained/logged in theMBMS information. The logging reason information may indicate that theMBMS information is information logged based on an event, such as alogging execution condition. The MBMS information may include MBMSservice failure reason information. The MBMS service failure reasoninformation may be indicative of an MBMS service reception failure.Furthermore, the MBMS service failure reason information may beindicative of a detailed reason (e.g., an MCCH acquisition failure or anSIB13 acquisition failure) for which the MBMS service reception failurehas occurred. The MBMS information may include logging time informationindicative of a point of time at which the MBMS information has beenlogged. Furthermore, the MBMS information may further include pieces oflower information that may be included in the MBMS information describedabove with reference to FIG. 17. The MBMS information obtained andlogged at step S1822 may be stored as a single log entry.

If the reception failure of the MBMS service continues to occur (S1831,S1841, S1851), the UE may periodically obtain and log MBMS informationat the specific logging interval T₁ within the logging duration T_(D)(S1832, S1842, S1852). At each point of time, the UE performs MBMSmeasurements in order to obtain the MBMS information. The UE may performwireless measurements on a frequency and/or subframe provided by an MBMSservice. The UE may include a measurement result in the MBMSinformation. Furthermore, the UE may include location informationindicative of the location of the UE in the MBMS information at a pointof time at which the MBMS information is obtained and logged.

Furthermore, the UE may include logging reason information indicative ofa reason for which the MBMS information has been obtained/logged in theMBMS information. The logging reason information may indicate that theobtained and logged MBMS information has been logged based on periodiclogging. Logging time information indicative of a point of time at whichcorresponding MBMS information has been logged may be include in each ofpieces of MBMS information. Furthermore, each piece of MBMS informationmay further include pieces of lower information that may be included inthe MBMS information described with reference to FIG. 17. MBMSinformation obtained and logged at each step may be stored as a singlelog entry.

When the logging duration T_(D) expires, the UE determines to stop theacquisition and logging of the MBMS information (S1860). The UE maydrive a timer in order to manage duration in which MBMS information isobtained and logged. The timer may be set as the logging duration T_(D).

The UE that has stopped the acquisition and logging of the MBMSinformation may report the logged MBMS information to the network. Tothis end, the UE may send a logged MBMS information availabilityindicator to the network in order to notify the network that the loggedMBMS information is present (S1871). The logged MBMS informationavailability indicator may be included in an RRC message andtransmitted. The logged MBMS information availability indicator may beincluded in an RRC connection establishment-complete message, an RRCconnection reconfiguration-complete message, an RRC connectionre-establishment-complete message, or an UE information message andtransmitted to the network. In this figure, the logged MBMS informationavailability indicator has been illustrated as being transmitted to theLTE cell. If the UE uses another cell as a serving cell, the UE may sendthe logged MBMS information availability indicator to the correspondingserving cell.

The LTE cell or another serving cell that has received the logged MBMSinformation availability indicator may send a logged MBMS informationreporting request that requests the reporting of the logged MBMSinformation to the UE (S1872). Thereafter, the UE may send the loggedMBMS information to the LTE cell or another serving cell in response tothe MBMS information reporting request (S1873).

In the example shown in FIG. 18, the acquisition and logging of the MBMSinformation by the UE has been performed for the logging duration T_(D).In this case, it is assumed that the UE has continuously failed inreceiving an MBMS service for the logging duration T_(D). If the UEnormally receives the MBMS service before the logging duration T_(D)expires, the satisfaction of the logging execution condition isreleased. Accordingly, the UE may obtain and log corresponding MBMSinformation and may determine to stop the acquisition and logging of theMBMS information. The MBMS information of a log entry logged at thispoint of time may include logging reason information. The logging reasoninformation may indicate that the logged MBMS information is informationlogged based on an event, such as a logging execution condition. TheMBMS information may include MBMS service failure reason information.The MBMS service failure reason information may be indicative of therecovery of an MBMS service reception failure. Furthermore, the MBMSservice failure reason information may be indicative of a detailedreason (e.g., a success in obtaining an MCCH or a success in obtainingSIB13) for which the MBMS service reception failure has been recovered.The MBMS information may include information indicative of a point oftime at which the MBMS information has been logged and/or informationindicative of the time for which the MBMS service failure has continued.Furthermore, the MBMS information may further include pieces of lowerinformation that may be included in the MBMS information described abovewith reference to FIG. 17.

In FIG. 18, the UE has stored the obtained and logged MBMS informationand reported a plurality of log entries to the network at once. However,a method of reporting, by the UE, MBMS information is not limited to themethod, and the UE may immediately report the MBMS information to thenetwork when it obtains the MBMS information. In the example of FIG. 18,the UE may obtain MBMS information at each of steps S1832, S1842, andS1851 and may immediately report the obtained MBMS information to thenetwork.

In the example of FIG. 18, the logging of the MBMS information by the UEmay be performed depending on the deterioration of MBMS servicereception quality unlike in the case where the logging of the MBMSinformation is performed depending on the MBMS service receptionfailure. Furthermore, unlike in the case where the acquisition andlogging of the MBMS information are periodically performed by the UE,the acquisition and logging of the MBMS information may be performedbased on an event related to a logging execution condition. Such anexample is described with reference to FIG. 19.

FIG. 19 is a diagram illustrating another example of a method ofreporting MBMS information in accordance with an embodiment of thepresent invention.

Referring to FIG. 19, an LTE cell is assumed to be an MBMS cell whichprovides UE with an interested MBMS service.

The UE receives an MBMS reporting configuration from the LTE cell(S1910). The MBMS reporting configuration may include a loggingexecution condition as MBMS logging execution information. The loggingexecution condition may be indicative of the deterioration of MBMSservice reception quality. In order to determine whether thedeterioration of the MBMS service reception quality has occurred, areception quality threshold may be set. The reception quality thresholdmay be previously set in the UE or may be set in the UE through an MBMSreporting configuration.

The LTE cell is an MBMS cell which provides the UE with an interest MBMSservice, and thus the UE may receive the MBMS service from the LTE cell(S1920).

While the UE receives the MBMS service from the MBMS cell, it may detectthe deterioration of MBMS service reception quality (S1931). In thiscase, the UE determines to log MBMS information and logs related MBMSinformation (S1932). The UE performs MBMS measurements in order toobtain the MBMS information. The UE may perform wireless measurements ona frequency and/or subframe provided by the MBMS service. The UE mayinclude a measurement result in the MBMS information. Furthermore, theUE may include location information indicative of the location of the UEin the MBMS information at a point of time at which the MBMS informationis obtained and logged.

Furthermore, the UE may include logging reason information indicative ofa reason for which the MBMS information has been obtained/logged in theMBMS information. The logging reason information may indicate that theMBMS information is information logged based on an event, such as alogging execution condition. The MBMS information may include MBMSservice deterioration reason information. The MBMS service deteriorationreason information may be indicative of the deterioration of MBMSservice reception quality. Furthermore, the MBMS service deteriorationreason information may be indicative of a detailed reason for which thedeterioration of the MBMS service reception quality has occurred. TheMBMS information may include logging time information indicative of apoint of time at which the MBMS information has been logged.Furthermore, the MBMS information may further include pieces of lowerinformation that may be included in the MBMS information described abovewith reference to FIG. 17. The MBMS information obtained and logged atstep S1932 may be stored as a single log entry.

The UE performs the acquisition and logging of MBMS information based onan event related to a logging execution condition. Accordingly, the UEmay obtain and log (S1932) MBMS information when the deterioration ofMBMS service reception quality occurs (S1931) and may not log MBMSinformation unless the satisfaction and/or release of the loggingexecution condition is generated (if the deterioration of the MBMSservice reception quality is not recovered).

The UE receives MBMS service of normal quality from the MBMS cell andmay detect that the deterioration of the MBMS service reception qualityhas been solved (S1941). In this case, the UE determines to stop thelogging of the MBMS information and logs related MBMS information(S1942). The UE performs MBMS measurements in order to obtain the MBMSinformation. The UE may perform wireless measurements on a frequencyand/or subframe provided by the MBMS service. The UE may include ameasurement result in the MBMS information. Furthermore, the UE mayinclude location information indicative of the location of the UE in theMBMS information at a point of time at which the MBMS information isobtained and logged.

Furthermore, the UE may include logging reason information indicative ofa reason for which the MBMS information has been obtained/logged in theMBMS information. The logging reason information may indicate that theMBMS information is information logged based on an event, such as alogging execution condition. The MBMS information may include MBMSservice deterioration reason information. The MBMS service deteriorationreason information may indicate that the deterioration of MBMS servicereception quality has been solved. The log entry may include informationindicative of a point of time at which the MBMS information has beenlogged and/or information indicative of the time for which thedeterioration of the MBMS service reception quality has continued.Furthermore, the MBMS information may further include pieces of lowerinformation that may be included in the MBMS information described abovewith reference to FIG. 17. The MBMS information obtained and logged atstep S1932 may be stored as a single log entry.

The UE that has determined to stop the acquisition and logging of theMBMS information may report the logged MBMS information to the network.To this end, the UE may send a logged MBMS information availabilityindicator to the network in order to notify the network that the loggedMBMS information is present (S1951). The logged MBMS informationavailability indicator may be included in an RRC message andtransmitted. The logged MBMS information availability indicator may beincluded in an RRC connection establishment-complete message, an RRCconnection reconfiguration-complete message, an RRC connectionre-establishment-complete message, or an UE information message andtransmitted to the network. In this figure, the logged MBMS informationavailability indicator has been illustrated as being transmitted to theLTE cell. If the UE uses another cell as a serving cell, the UE may sendthe logged MBMS information availability indicator to the correspondingserving cell.

The LTE cell or another serving cell that has received the logged MBMSinformation availability indicator may send a logged MBMS informationreporting request that requests the reporting of the logged MBMSinformation to the UE (S1952). Thereafter, the UE may send the loggedMBMS information to the LTE cell or another serving cell in response tothe MBMS information reporting request (S1953).

In the example shown in FIG. 19, the execution of the acquisition andlogging of the MBMS information by the UE has been stopped when thesatisfaction of the logging execution condition is released (S1941), butmay not be limited thereto. If logging duration T_(D) has been set inthe MBMS reporting configuration, the UE may obtain and log MBMSinformation for the logging duration. In the example of FIG. 19, iflogging duration has been set, if the deterioration of MBMS servicereception quality has not been solved within the logging duration, theUE may determine to stop the logging of MBMS information when thelogging duration expires.

In FIG. 19, the UE has stored obtained and logged MBMS information andreported a plurality of log entries to the network. However, a method ofreporting, by the UE, MBMS information is not limited thereto. The UEmay immediately report MBMS information to the network when it obtainsthe MBMS information. In the example of FIG. 19, the UE may obtain MBMSinformation at each of steps S1932 and S1942 and immediately send theobtained MBMS information to the network.

In accordance with the method of reporting MBMS information according toan embodiment of the present invention, UE configured to report MBMSinformation may obtain and log the MBMS information depending on thereception status or reception quality of an MBMS service. Accordingly, aproblem in which unnecessary power is consumed because UE obtains andlogs MBMS information in the situation in which an MBMS service notrelated to the UE is provided or the UE is not provided with an MBMSservice can be prevented. Furthermore, signaling overhead can be reducedand use efficiency of radio resources can be improved becauseunnecessary signaling for the MBMS information reporting of UE can beprevented.

FIG. 20 is a block diagram illustrating a wireless device in which anembodiment of the present invention is implemented. The device may beimplemented using UE or a network system for performing a method inaccordance with an embodiment of the present invention.

Referring to FIG. 20, the wireless device 2000 includes a processor2010, memory 2020, and a Radio Frequency (RF) unit 2030. The processor2010 implements the proposed functions, processes and/or methods. Theprocessor 2010 may be configured to generate and provide an MBMSreporting configuration for the acquisition/logging and reporting ofMBMS information. The processor 2010 may be configured to perform theacquisition/logging and reporting of MBMS service information. Theprocessor 2010 may be configured to perform the embodiments of thepresent invention described with reference to FIGS. 17 to 19.

The RF unit 2030 is connected to the processor 2010, and sends andreceives radio signals.

The processor may include Application-Specific Integrated Circuits(ASICs), other chipsets, logic circuits, and/or data processors. Thememory may include Read-Only Memory (ROM), Random Access Memory (RAM),flash memory, memory cards, storage media and/or other storage devices.The RF unit may include baseband circuits for processing radio signals.When the embodiment is implemented in software, the aforementionedscheme may be implemented as a module (process or function) thatperforms the aforementioned function. The module may be stored in thememory and executed by the processor. The memory may be placed inside oroutside the processor and may be connected to the processor using avariety of well-known means.

In the above exemplary systems, although the methods have been describedon the basis of the flowcharts using a series of the steps or blocks,the present invention is not limited to the sequence of the steps, andsome of the steps may be performed at different sequences from theremaining steps or may be performed simultaneously with the remainingsteps. Furthermore, those skilled in the art will understand that thesteps shown in the flowcharts are not exclusive and may include othersteps or one or more steps of the flowcharts may be deleted withoutaffecting the scope of the present invention.

What is claimed is:
 1. A method of reporting, by user equipment,Multimedia Broadcast and Multicast Service (MBMS) information in awireless communication system , the method comprising: determiningwhether or not to execute a logging of the MBMS information; logging theMBMS information if the logging is determined to be performed; andreporting the logged MBMS information to a network, wherein whether ornot to execute the logging of the MBMS information is determined basedon an MBMS information logging execution condition, and the MBMSinformation logging execution condition comprises at least one of areception failure of an MBMS service and reception quality of the MBMSservice provided by the network.
 2. The method of claim 1, whereindetermining whether or not to execute the logging of the MBMSinformation comprises determining to execute the logging if the MBMSinformation logging execution condition is satisfied.
 3. The method ofclaim 2, further comprising: determining whether or not to stop theexecution of the logging of the MBMS information.
 4. The method of claim2, wherein determining whether or not to stop the execution of thelogging of the MBMS information comprises determining to stop theexecution of the logging if the MBMS information logging executioncondition that has been satisfied is released.
 5. The method of claim 4,wherein logging the MBMS information comprises: logging a first MBMS logentry if the MBMS information logging execution condition is satisfied;and logging a second MBMS log entry if the MBMS information loggingexecution condition is not satisfied, wherein the logged MBMSinformation comprises the first MBMS log entry and the second MBMS logentry.
 6. The method of claim 5, wherein the first MBMS log entrycomprises information indicating that the first MBMS log entry has beenlogged because the MBMS information logging execution condition has beensatisfied.
 7. The method of claim 6, wherein the second MBMS log entrycomprises information indicating that the second MBMS log entry has beenlogged because the satisfaction of the MBMS information loggingexecution condition has been released.
 8. The method of claim 5, whereinlogging the MBMS information comprises periodically logging third MBMSlog entries until the satisfaction of the MBMS information loggingexecution condition is released after the MBMS information loggingexecution condition is satisfied, wherein the logged MBMS informationfurther comprises the third MBMS log entries.
 9. The method of claim 8,wherein each of the third MBMS log entries comprises informationindicating that a corresponding third MBMS log entry has beenperiodically logged.
 10. The method of claim 1, further comprisingreceiving an MBMS reporting configuration comprising configurationinformation for the logging and reporting of the MBMS information by theuser equipment from the network, wherein the MBMS reportingconfiguration comprises MBMS logging execution information whichspecifies the MBMS information logging execution condition.
 11. Themethod of claim 1, wherein reporting the logged MBMS information to thenetwork comprises: sending a logged MBMS information availabilityindicator indicating that the logged MBMS information to be reported tothe network is present to the network; receiving a logged MBMSinformation reporting request which requests the reporting of the loggedMBMS information from the network; and sending a logged MBMS informationreport comprising the logged MBMS information to the network in responseto the logged MBMS information reporting request.
 12. The method ofclaim 1, wherein reporting the logged MBMS information to the networkcomprises immediately sending the logged MBMS information to the networkin response to the logging of the MBMS information.
 13. A wirelessdevice operating in a wireless communication system, the wireless devicecomprising: a Radio Frequency (RF) unit which sends and receives radiosignals; and a processor which is functionally coupled to the RF unitand operates, wherein the processor is configured to: determine whetheror not to execute a logging of the MBMS information; log the MBMSinformation if the logging is determined to be performed; and report thelogged MBMS information to a network, wherein whether or not to executethe logging of the MBMS information is determined based on an MBMSinformation logging execution condition, and the MBMS informationlogging execution condition comprises at least one of a receptionfailure of an MBMS service and reception quality of the MBMS serviceprovided by the network.